1. Field of the Invention
The present invention relates to black reflective metal coatings, and to decorative products including laminates, having such coatings as part thereof.
2. Description of the Prior Art
Recent changes in the construction and the appearance of automobiles due in part to the increase in cost of automotive metals, has encouraged efforts to develop and employ synthetic resin materials, as metal substitutes where possible. For example, numerous metalized resin parts have been adopted as replacements for conventional chromium plate in external trim work, bumpers and the like, to reduce vehicle weight, and to reduce the cost of manufacture and operation of the automobile.
Recently, exterior trim work has made broad use of glossy black coloration in place of the standard chrome-plated appearance. Specific parts have been prepared with the objective of presenting a glossy black appearance, however having the reflectance of chromium. This product has been appropriately nicknamed "black chrome" as it seeks to combine the black pigmentation with the reflective metallic properties of chromium plate.
So far as is known, the preparation of parts with the "black chrome" finish has involved the direct application of various coating systems involving either composite paints, or sequential coatings of reflective material and translucent paints, to achieve the black reflective effect. For example, the formed part may be metalized in accordance with conventional commercial procedures, and thereafter coated with a black paint that offers a translucent appearance permitti.ng the underlying reflective metal layer to be visible. This effect may be achieved either by the application of an extremely thin black paint, or the preparation of a paint containing a reduced quantity of pigment loading based on resin solids.
An alternate approach has been to include the reflective material within the paint formulation, by the inclusion of micron sized metal particles in a uniform, almost colloidal suspension in combination with pigment particles of comparable size. In such instance, the formed part would receive a succession of thin coatings of this specially formulated paint for the purpose of achieving the combination of black color and reflectance.
The products prepared by the described techniques possess certain drawbacks, among them an undesirably short useful life. Many of the products prepared with the "black chrome" finish are utilized in external applications where adverse mechanical and environmental conditions promote deterioration. The paints frequently break down, fade and otherwise discolor after extended exposure to sunlight, and frequently fracture upon mechanical impact, even in the instance where purportedly protective top coats are applied. The paints themselves frequently exhibit poor uniformity between batches, with the result that the finished products may vary in hue, reflectance, etc.
The prior art products possess a further drawback, in that the specialized nature of the coatings applied to create the "black chrome" effect, must be individually and directly applied to the formed products. The individual coating of respective parts after their formation, demands greater time and facilities, that contributes to an undesirable increase in manufacturing cost.
A need therefore exists for the development of a black reflective product that is capable of low cost manufacture, such as by hot transfer lamination, and exhibits improved mechanical strength and resistance to environmental deterioration lacking in the prior art products.